The present plant practice for the production of uranium oxides from uranium-bearing ores involves a complex, multi-stage operation. The ores, which generally contain uranium in an amount of 200 to 1000 ppm undergo a primary crushing followed by fine grinding normally to a particle size of 200 mesh. The finely ground ore is mixed with a lixiviant to form a slurry and allowed to react to extract the uranium from the ore into solution in the lixiviant. The normal lixiviants are dilute sulphuric acid or an alkali, e.g. sodium or ammonium carbonate.
The pregnant leach liquors are purified and concentrated by ion exchange and/or solvent extraction followed by chemical treatment to precipitate the diuranate. The solid diuranate is separated from the liquid and calcined to yield the uranium oxide, known as yellow cake.